Pump plunger



sa., ad Dec. 5, 1939A UNITED STATES PATENT OFFICE Application June v6, 1936, Serial No. 83,876

3 Claims.

:I'his invention has to do in a general way with pumps of the type used in oil well operations and is more particularly related to improvements in the construction of the plungers for such pumps.

It is a primary object of this invention to produce a pump plunger of the general class described above which is provided with a surface coating formed of hard metal plate such as chromium plate having a very high wear resistance w whereby the operating life of the plunger is greatly prolonged.

In the development of the plated plunger contemplated by this invention attempts were iirst made to merely plate the plunger throughout its full length. These plungers, as is well known to those familiar with the art, are provided with internally threaded end portions or boxes adapted to receive bushing members which go to make vup the plunger assembly and it was discovered that a plunger plated in the general manner described above expanded a sufdcient amountat its ends to crack the very brittle and very thin hard metal plate which was followed by peeling or chipping of the plate metal which galled the pump plunger and scored the pump liners. In this conection it is a primary object of this invention to provide a plated plunger of the class described which is so formed and in which the plate metal is so applied as to eliminate the poso sibility of the plate metal being cracked or broken by the expansion of the box region in the plunger when the bushing member is inserted.

It is a further object of this invention to provide a plated surface of the class described which. 5 in certain preferred forms of my invention, is applied so as not to have an exposed end portion Vin rubbing engagement with the. plunger barrel or liner therein. This further insures the plate metal against peeling or breakage and in addi- 40 tion guards against the intrusion of corrosive substances between the plate metal and the body of the plunger.

Details in the construction of certain preferred forms of my invention, together with other ob- 45 jects attending its production will be best understood from the following description of the accompanying drawing which are chosen for illustrative purposes only and in which:

Fig. 1 is an elevational view partly in section 50 illustrating a pump plunger equipped with a preferred embodiment of my'invention;

Fig. 2 is an enlarged fragmentary sectional ele- -vation illustrating more clearly the manner in which the plate metal is applied to the plunnger;

55 Fig. 3 is an enlarged fragmentary sectional elevation similar to Fig. 2 but showing a modied form of the invention; and i Fig. 4 is a sectional elevation similar to Figs. 2 and 3 showing still another modied form of the invention. 5

More particularly describing the invention as herein illustrated, reference numeral II indicates a pump plunger which has an elongated hollow plunger section indicated by reference numeral' I2. The plunger section I2 is formed with inter- 10 nally threaded end portions I3 and rIl which constitute boxes for the reception of ttings or bushing members generally indicated by referencenumerals I5 and I6 respectively. The bushing member or fitting I5 constitutes a portion of a 15 Working valve assembly of any conventional type generally indicated by reference numeral I8, such assembly being connected at its upper end to an operating rod Ill.y The lower fitting I6 constitutes a bushing member conventionally desig- 20 nated as the lower plunger inut of any conventional type which contains an opening for the passage of a Garbutt rod 20.

Inthe form of my invention shown in Fig. 1, the outer surfaceof the main plunger section I2 25 in the regions of the inner ends of theboxes I3 and I4 is provided with annular grooves or channels indicated by reference numerals/2| and 2i'. These grooves or channels are situated inwardly toward each other from the innermost end of the boxes I3 and I4 and serve the dual purpose of iirst, permitting such expansion as is occasioned through the reception of the bushing members in the respective boxes to take place in that portion of the plunger surrounding the boxes only without disturbing the wall metal on the side of the grooves opposite the boxes and, second, providing channels for the reception of the end portions of the plate metal coating about to be described.

The region of the -plunger between the grooves 2I and 2l is provided with a thin coating of hard metal plate such as chromium, such coating being indicated in Fig. 2 by reference numeral 23. It will be observed from Fig. 2 that the end of the plate metal lterminates within the groove or channel 2|, as indicated at 24. It Will also be observed that the plane in which this plate metal terminates indicated at A is preferably situated a slight distance away from the plane in which the threads 2l of the box terminate, this last men- 50 tioned plane being indicated by the letter B.

In other words, the plate metal as applied to the plunger contemplated by this invention terminates at a point short of the region of the Y plunger occupied by the box so that any expansion which takes place in the end portion of the plunger by virtue of a bushing member being received in this box is ineffective in applying an expansive stress to the metal plate.

In the form of my invention shown in Fig. 3 I provide a plunger construction in which the end portion of the plunger. surrounding the threads 21' is turned down to a diameter slightly less than the diameter of the main portion of the plunger, thereby providing a shoulder It which is situated in a plane A' at or below the plane B' in which the threads 2 1 terminate. 'I'he plate metal 23" in this form of my invention `covers the portion of the plunger between the two shoulders corresponding to .the shoulder 8l' which are formed at opposite ends of the plunger in this construction. In this form of my invention, like the form shown in Hg. 2. the plate metal terminates onv a portion ofthe plunger of less diameter than the main body portion which it covers and in .this way any possible peeling action from the end of the plate metal and possible intrusion of corrosive substances between the plate metal and the wall metal of the plunger is avoided.

In the form of my invention shown in Fig. 4 I show the simplest type of construction contemplated by this invention in which the possibility of cracking in the plate metal due to the expansive force pointed out above is eliminated merely by terminating the plate metal 2l" in a -plane A" which is shown as beingvlocated below the plane B" in which the threads 21" terminate and which is more properly described as terminating at a point below the region in which the expansive stresses are set up by the reception of a bushing member in the box.

In all forms of my invention the plate metal on the outer surface of the plunger may be applied in any conventional manner such as through the use of an eiectroiytic process, the end portions of the plunger being protected during the plating operation by nrst coating these portions with an insulating material such as wax or a suita,isa,sav

ehie insulating paint, whereby an unpiaied er exposed region is obtained.

It ie te he understood that while 1 have herein described and illustrated certain preferred forms of my invention and have hereinabove referred to one specific metal as a preferred plating metal,

that various modifications of the invention may Y of reduced diameter thereby forming shoulders on the outer surface adiacent the inner ends of said boxes; and a surface coating of hard metal plate on the exterior of said plunger between said shoulders, said plate metal extending over said A shoulders and terminating between said shoulders and the inner ends of said box portions. v

2. As an article of manufacture, a plungerfor use in a pump comprising a tubular member having internally threaded end portions for the reception of threaded fittings, having an external annular groove at each end substantially opposite the inner termini of the threads of the respective threaded end portions, and having an external coating of hard metal plate between said grooves and terminating in said grooves, the end portions of said member being unplated.

3. As an article of manufacture. a plunger fox` use in a pump comprising a tubular member having internally threaded end portions, having a portion of reduced diameter on the outer surface in the region of each end, and having an` external coat of hard metal plate between said reduced portions, the ends of said coat being respectively located on said reduced portions whereby the end edges of said coat are of less diameter than the remainder of said coat.

SUMNER. B. SARGENT, Ja. 

